This proposal is to investigate the interrelationship between the behavior of children with chronic illness, the behavior of other family members and the subsequent role of medical and psychological intervention in altering identified behavioral pathology within each family system. In addition, comparisons will be made between family environments of chronically ill children and those of behaviorally aberrant children and normal children. Finally, the developmental impact of the chronic illness on the child and the family will be investigated by controlling for the duration of the disease (cross-sectional design) and through repeated measures of the same family system over a four (4) year period (longitudinal design). The experimental design will permit inter- and intra-group analysis as well as within family, single subject design techniques where the child acts as his own control.